Various types of gate mechanisms have been devised for particular types of conveyors. Conveyors with a generally tubular construction, such as screw conveyors and conveyors of the type disclosed in U.S. Pat. No. 3,586,155, may employ a rotary gate mechanism to either allow product to discharge through the opened gate or to move product downstream from the closed gate. Various types of rotary gate mechanisms are disclosed in U.S. Pat. Nos. 1,401,155, 3,074,534, 3,077,975, and 3,342,315. U.S. Pat. No. 4,023,675 discloses a slide door for use with a chain conveyor. U.S. Pat. No. 3,731,787 discloses a slide gate with sensors.
An increasingly common type of conveyor utilizes a substantial planar tray floor and a cyclically powered drive mechanism cyclically powered to move the goods along the tray floor. One type of conveyor which utilizes such a cyclically powered tray is a vibratory conveyor, and another type of conveyor which uses a similar cyclically powered tray is a linear motion conveyor. Both vibrating and linear motion conveyors commonly employ a substantially planar tray floor with opposing sides, and thus are sometimes referred to as a trough-type conveyor. The stroke in a vibratory conveyor is relatively short, and typically is approximately 1/16th of an inch, so that the tray imparts an upward and forward motion to the goods. The tray is returned to its original position while the goods are out of contact with the tray floor. A linear motion conveyor has a much longer stroke, typically in the range of approximately an inch and a half, and moves the goods slowly forward and returns the tray quickly while the goods slide along the tray floor. A slide gate for a trough-type conveyor is disclosed in U.S. Pat. No. 2,716,741. More complex and specialized types of gates for conveyors with a planar tray floor are disclosed in U.S. Pat. Nos. 3,042,360, 3,315,792, and 3,511,303.
Conventional gate mechanisms for conveyors with a planar tray floor have various problems which have limited their acceptance in the industry. Traditional gate mechanisms are intended to operate in the fully opened or fully closed position. This limitation prevents equipment downstream from the conveyor from receiving a steady flow of product, and thus results in poor production efficiency. Some conveyor manufacturers have attempted to overcome this problem by utilizing triangular shaped cutouts in the conveyor floor and allowing the gate mechanism to be positioned at selected intervals between the fully opened and fully closed position. The use of such triangular shaped cutouts requires a great deal of space along the length of the conveyor, and also requires a linear actuator which is capable of sliding the gate over a relatively long movement.
A significant problem with conventional gate mechanisms for trough-type conveyors with a planar tray floor involves the inability of the gate to completely seal in the closed position. Trough-type conveyors are commonly used to transport snack foods and fine particles associated with such goods have caused a growing problem when high hygiene is critical. Some companies have required specialized devices to prevent unwanted particles, such as dust associated with a transported goods, from leaking out of a closed gate and into another product line. Many slide gates associated with trough-type conveyors have a difficult time sealing the gate area when in the closed position because product is passing through a gate while it is being closed. The product may thus become jammed in the gate sealing area, resulting in both product breakage and the buildup of material to prevent complete gate closing. A related problem is that the gate seal is commonly exposed to the product when the gate is partially or fully opened. As the product passes by the gate seal, the sealing material is worn and thus prevents a reliable seal from substantially being formed when the gate is in the closed position.
The disadvantages of the prior art are overcome by the present invention, and an improved gate mechanism is hereinafter disclosed for a trough-type conveyor. The gate mechanism of the present invention may be used on either vibratory conveyors or horizontal motion conveyors. The improved gate mechanism has a long life and a reliable operation.